Ducted support housing assembly

ABSTRACT

A method is disclosed of making an integral structure comprised of inner and outer coaxial shells mutually supported so as to define an annular passageway between the shells. The integral structure may be an air inlet housing for a gas turbine engine and the inner shell may be a hub member having a generally cylindrical passage extending therethrough for rotatably receiving a drive shaft. The inner shell is formed by braiding on a shaped mandrel a plurality of fibers such as fiberglass, boron, carbon, or the like, to form an inner shell preform having an outer surface of revolution. A plurality of duct preforms are similarly formed on a conical mandrel, then removed, and administered onto an outer peripheral surface of a duct mold so as to define a modified shape. The modified duct preforms are then positioned onto the outer surface of the inner shell preform in side-by-side relationship such that the first and second lateral surfaces on adjacent modified duct preforms are coextensive and engaged, the plurality of modified duct preforms completely circumscribing the inner shell preform. Then, a plurality of fibers are braided across the plurality of outer modified duct surfaces of the duct preforms to form an outer shell preform spaced from and coaxial with the inner shell preform. Thereafter, resin is applied to the structure to encapsulate the braided inner shell preform, the braided modified duct preforms, and the braided outer shell preform. The resin is then cured to thereby complete fabrication of the integral structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to components fabricated from braidedfiber composite materials and, in particular, to a method of making anintegral structure so fabricated comprised of inner and outer coaxialshells mutually supported so as to define an annular passagewaytherebetween. Throughout the instant disclosure, the terms "braidedfiber" or "braiding" are intended to include "woven or knitted fabric"or "weaving" or "knitting", although the specific construction ofbraided fiber and the specific method of braiding are considered to bepreferable to the specific constructions of woven or knitted fabrics andthe specific methods of weaving and knitting.

2. Description of the prior Art

It is known to utilize elongate material, such as boron fibers, carbonfibers, and glass fibers for the reinforcement of gas turbine enginecomponents such as compressor and turbine blades and vanes. Inparticular, the potential for usage of high modulus, high strengthfibers, such as carbon, silicon carbide, boron, and glass in a resin ormetal matrix is widely recognized. A typical application of suchmaterials is disclosed in U.S. Pat. No. 5,018,271 to Bailey et al. Inthat particular instance, a composite gas turbine engine blade isdisclosed as being made by braiding a plurality of fibers to form apreform. After braiding, the preform is placed in a mold provided with ablade shaped cavity and is subjected to matrix infiltration while themold halves are pressed together by suitable pressing means such as ahydraulic cylinder. The goal of the present invention is to utilize asimilar technique for the construction of a component which heretoforehas only been constructed of metal, namely, magnesium, aluminum and,more recently, titanium and steel.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a method is disclosed ofmaking an integral structure comprised of inner and outer coaxial shellsmutually supported so as to define an annular passageway between theshells. The integral structure may be an air inlet housing for a gasturbine engine and the inner shell may be a hub member having agenerally cylindrical passage extending therethrough for rotatablyreceiving a drive shaft. The inner shell is formed by braiding on ashaped mandrel a plurality of fibers such as glass, boron, carbon, orthe like, to form an inner shell preform having an outer surface ofrevolution.

A plurality of duct preforms are similarly formed on a desired shape ofmandrel (conical, for example), then removed, and administered onto anouter peripheral surface of a duct mold so as to define a modifiedshape. As modified, each duct preform is comprised of an inner ductsurface shaped to congruently mate with the outer surface of the innershell preform, an outer duct surface spaced from the inner duct surfaceand first and second lateral walls having opposed lateral surfaces. Theduct preforms are then positioned onto the outer surface of the innershell preform in side-by-side relationship such that first and secondlateral surfaces on adjacent duct preforms are coextensive and engaged,the plurality of duct preforms completely circumscribing the inner shellpreform.

Then, a plurality of fibers are braided (or placed on a preform) acrossthe plurality of the outer duct surfaces to form an outer shell preformspaced from and coaxial with the inner shell preform. Thereafter, resinis applied to the structure to encapsulate the braided inner shellpreform, the braided duct preforms, and the braided outer shell preformand the resin is then cured to thereby form the integral structure.

A broad objective of the invention is to exploit the advantages offeredby emerging organic matrix composites technology by tailoring resinsystems to mold lightweight, low cost, engine components. A morespecific objective is to achieve a structure which will exhibit thegreatest possible strength between an inner shell and an outer shellwith a plurality of circumferentially spaced integral strut membersdefining ducts while avoiding stress concentrations where the strutmembers join with the outer shell and with the inner shell. With thisend in mind, an inlet housing for a gas turbine engine is sought whichwill outperform its magnesium or aluminum counterparts, specificobjectives being to eliminate corrosion and reduce weight by at least15% relative to an equivalent aluminum part.

A primary object of the invention, then, is to provide a ducted inlethousing assembly for a gas turbine engine which is an integral structurecomprised of inner and outer coaxial shells mutually supported so as todefine an annular passageway therebetween.

Another object of the invention is to provide such an integral structurewhich is not subject to corrosion, which is substantially lighter inweight, and which requires less maintenance than conventionalconstructions.

A further object of the invention is the provision of such an integralstructure fabricated from braided fiber composition materials.

Still another object of the invention is the provision of such astructure which can be more economically manufactured operated, andmaintained.

Yet a further object of the invention is to provide such a constructionin which repeatability of manufacture can be assured and which assuresuniform load transfer along the periphery of the structure. Stillanother object of the invention is to provide such a construction whichcan tolerate substantial damage, including ballistic damage, handlingdamage and the like without losing its effectiveness. Still anotherobject of the invention is the provision, at leading and trailing endsof the inner and outer coaxial shells of metallic annular end plateswhich contain provision for fastening the structure to other componentsof the gas turbine engine.

Other and further features, advantages, and benefits of the inventionwill become apparent in the following description taken in conjunctionwith the following drawings. It is to be understood that the foregoinggeneral description and the following detailed description are exemplaryand explanatory but are not to be restrictive of the invention. Theaccompanying drawings which are incorporated in and constitute a part ofthis invention, illustrate one of the embodiments of the invention, and,together with the description, serve to explain the principles of theinvention in general terms. Like numerals refer to like parts throughoutthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view diagrammatically illustrating a gas turbineengine utilizing an inlet housing embodying the present invention;

FIG. 2 is a perspective exploded view of certain components illustratedin FIG. 1;

FIG. 3 is an elevational cross section view illustrating fabrication ofone component of the invention;

FIGS. 4A and 4B are detail cross section views illustrating parts ofFIG. 3;

FIGS. 5A, 5B, and 5C are detail perspective views diagrammaticallyillustrating steps used in the fabrication of another component of theinvention;

FIG. 5D is a detail cross section view of FIG. 5C;

FIG. 6 is a perspective exploded view illustrating a further step in theprocess of the invention;

FIG. 7 is a perspective view illustrating yet another step in theprocess of the invention;

FIG. 7A is a perspective view illustrating the completed fabrication ofan inlet housing preform according to the invention;

FIG. 8 is a cross section view, in elevation, illustrating yet a furtherstep in the process of the invention;

FIG. 9 is a perspective view of a completed inlet housing fabricated inaccordance with the invention;

FIG. 10 is a cross section view taken generally along line 10--10 inFIG. 9; and

FIG. 11 is a front elevation view of the inlet housing illustrated inFIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turn now to the drawings, and, initially, to FIGS. 1 and 2 whichillustrate a typical gas turbine engine 20 incorporating an inlethousing 22 embodying the present invention. Originally, the inlethousing 22 was fabricated from magnesium. However, because ofdifficulties experienced with that metal including its flammability, itscorrosiveness and other drawbacks, its use in new applications has beendiscontinued or restricted. Specifically, the incorporation of toxicsubstances in magnesium alloys to enhance its strength and otherproperties has recently become prohibited. As a result, aluminum andtitanium have become the materials of choice, but the added weight ofaluminum and titanium as compared to magnesium has had a detrimentaleffect on the overall performance of the engine. By reason of recentimprovements in organic matrix composite technology and in braidingtechniques, it has been found to be possible to produce the inlethousing 22 in a manner which eliminates problems of corrosion, canreduce weight by 10-20 percent relative to magnesium or up to 50 percentrelative to the part fabricated from aluminum, and to carry loads in anengine which has an output approximately 40 percent greater than that ofits predecessor.

The inlet housing 22 of the invention includes inner and outer coaxialshells 24, 26 respectively, which are mutually supported so as to definean annular passageway 28 between them. With the aid of a mounting plate30 which can be suitably attached to the inner shell 24, an output group32 is receivable within a generally cylindrical passage 34 extendingthrough the inner shell 24, as a hub member, and is suitably attached tothe inner shell. The output group 32 includes forward and aft bearingsand bearing supports 36, 38 respectively, which, in turn, rotatablysupport a drive shaft 40 which is part of a power output train of theengine 20 connected with the power turbine (not shown) via appropriatemechanical means.

Turn now to FIGS. 3, 4A and 4B for a description of the fabrication ofthe inner shell 24. A plurality of fibers 42 which may be, for example,glass, carbon, boron, or aramid, for example, KEVLAR brand fibers arebraided in a known manner on a shaped mandrel 44. The braided fibers 42may be laid down in a single course or in multiple courses, as desired.The mandrel 44 may be of any desired shape but, in FIG. 3, isillustrated as being generally cylindrical but smoothly tapering from afirst end 46 to a second end 48. In any event, an outer surface 50 ofthe mandrel 44 is substantially a surface of revolution.

In a preferred construction, as illustrated more clearly in FIGS. 4A and4B, a first course of fibers 52 is braided onto the outer surface 50 ofthe mandrel 44. In the course of the braiding process, a first annularmetallic end plate 54 may be positioned on the first course of fibers 52adjacent the first end 46 of the mandrel 44. At substantially the sametime, a second annular metallic end plate 56 may be positioned on thefirst course of fibers 52 adjacent the second end 48 of the shapedmandrel 44. The braiding process then continues such that the braidedfibers 42 intertwine and encircle the first and second end plates 54, 56and thereby apply a second course of fibers 58 eventually overlying thefirst course of fibers 52. Suitable light weight filler material 60which may be a polymer foam, for example, may be provided between thefirst and second courses 52, 58 and extending between the first andsecond end plates 54, 56, so as to avoid small radius curves in thefirst and second courses of fibers which would result in regions of highstress concentration. It will be understood that while, for theconstruction just described, there must be at least one course of fiberscomprising the first course 52 and at least one course of fiberscomprising the second course 58, there may, in actual fact, be many suchcourses should that be the desired construction. Additional fillermaterial or a structural strengthening circumferential layer asindicated at 62 (FIG. 4A) and 64 (FIG. 4B) may also be provided for thestructure of the inner shell 24 in order to avoid stress concentrations.Although the filler material 62 and 64 would preferably be applied bymeans of braiding, it may be applied using other techniques such as byplacement of a metallic ring or by use of a continuous fiber wind and itmay be comprised of material other than glass, carbon, and boron fibers.The end plates 54, 56 are preferably provided with a plurality ofcircumferentially spaced tapped holes 66, 68, respectively, to receivestuds 70 (FIG. 2) or other suitable fasteners for the purpose ofattaching the mounting plate 30 or other components to the inner shell24. Upon the completion of the braiding operation as depicted in FIGS.3, 4A, and 4b, the braided fibers 42 actually define an inner shellpreform 71 (FIG. 6) which, like the mandrel 44, has an outer surfacewhich is substantially a surface of revolution. The first end ring orannulus plate 54 defines a leading end of the resulting inner shellpreform 71 and the second end ring or annulus plate 56 defines atrailing end of the inner shell preform.

Turn now to FIGS. 5A, 5B, 5C, and 5D for a description of thefabrication of a plurality of duct preforms 72 (FIG. 5C and 6), aplurality of which will be integrated with the structure which resultsin the inlet housing 22. To this end, a plurality of fibers 74 arebraided in the manner previously employed with respect to the innershell preform 71 on a generally conical mandrel 76 to form an initialduct preform 78 (FIG. 5B) having a conical shape which is congruent withthat of the mandrel 76. Upon completion of the braiding operation, theinitial duct preform 78 is removed from the conical mandrel 76 (see FIG.5B). Then it is administered onto the outer peripheral surface of a ductmold 80 (FIG. 5C) so as to contiguously conform to the shape of the ductmold and thereby define a modified shape of the initial duct preform 78.As modified, viewing FIG. 6, each modified duct preform 72 includes aninner duct surface 82 shaped to congruently mate with the outer surface84 of the inner shell preform 71, an outer duct surface 86 spaced fromthe inner duct surface 82, and spaced apart lateral walls 88, 90 havingopposed lateral surfaces 92, 94, respectively.

Later in the process, but not at this time, after each modified ductpreform 72 will have attained the shape of the duct mold 80, it is thenremoved. As seen in FIG. 5D, the duct mold 80 may, for convenience andpracticality, be actually comprised of three components for ease ofremoval of the duct preform 72. As illustrated, the duct mold 80includes a central, substantially rigid member 96 and a pair ofpreferably resilient side members 98, 100 which actually contact thefibers of the duct preform 72. As illustrated, upon removal of thewedge-shaped central member 96, the side members 98, 100 can then bereadily slipped out of the duct preform 72. Of course, it will beappreciated that numerous other constructions of the duct mold 80 can beutilized and that the construction described is only for purposes ofexplanation. After formation of a plurality of duct preforms 72 on theirassociated duct molds 80, the duct preforms, together with theirassociated duct molds, are administered onto the outer peripheralsurface 84 of the inner shell preform 71 (see FIGS. 6 and 7). With theirinner duct surfaces 82 in mating engagement with the outer peripheralsurface 84 of the inner shell preform, the modified duct preforms 72 arepositioned in a side-by-side relationship at desired forward and aftlocations on the inner shell preform and such that the lateral surfaces92, 94 on adjacent modified duct preforms are coextensive and engaged.As seen in FIG. 7, the plurality of the modified duct preformscompletely circumscribe the inner shell preform.

Thereupon, as indicated in FIG. 7, a plurality of fibers 102 are braidedacross the outer duct surfaces 86 (or onto a similarly shaped mandrel)and completely circumscribe the modified duct preforms 72 which, inturn, completely circumscribe the inner shell preform 71. By so doing,an outer shell preform 104 is produced spaced from and coaxial with theinner shell preform. See FIG. 7A.

In this manner, fabrication of an inlet housing preform 106 asillustrated in FIG. 8 is completed, being an integral structurecomprised of the inner shell preform 71, the plurality of modified ductpreforms 72, and the outer shell preform 104. At this stage, however,the inlet housing preform 106 continues to envelop the shaped mandrel 44and the duct molds 80. Thereupon, an outer mold 108 is administered tothe outermost surface of the outer shell preform 104 so as to be incontiguous engagement therewith. Additional insert molds 110, 111 arepositioned at a forward end of the inlet housing preform 106 to assure avoid in that region following the next step of the process which isabout to be described. It will be appreciated that the upper portions ofFIG. 8 correspond to the forward portions of the inlet housing preform106. Thereupon, a forward end cap 112 which is annularly shaped isplaced in contiguous engagement with the outer mold 108, the insertmolds 110, 111, and the shaped mandrel 44. In similar fashion, a rearend cap 114 is placed in contiguous engagement with the trailingportions of the inlet housing preform 106 and, more specifically, withthose associated regions of the outer mold 108, duct molds 80, andmandrel 44. The entire structure thus described is then supportedbetween forward and rear press plates 116, 118, respectively, tomaintain the entire structure in an integral relationship.

Thereafter, suitable resin is applied, under suitable pressure, throughaligned apertures 120, 122 in the press plate 118 and rear end cap 114,respectively and thereby into the interstices of the braided fibers inthe entire inlet housing preform 106. The resin is applied until allvoids within the inlet housing preform are filled. The entire structureillustrated in FIG. 8 is then placed in a suitable oven and the resincured to thereby form an integral structure in the nature of the inlethousing 22 as illustrated in FIG. 9. The inlet housing 22 illustrated inFIG. 9 results upon removal of the pressplates 116, 118, the end caps112, 114, the mandrel 44, the duct molds 80, the insert molds 110, 111,and the outer mold 108. As previously described, the inlet housing 22 iscomprised of the inner shell 24 and the outer shell 26. A plurality ofcircumferentially spaced strut members 124 result from the adjoininglateral walls 88, 90 of the juxtaposed modified duct preforms 72. Thepassageways 28 result from the spacing between the inner shell 24, theouter shell 26, and the strut members 124.

While preferred embodiments of the invention have been disclosed indetail, it should be understood by those skilled in the art that variousother modifications may be made to the illustrated embodiments withoutdeparting from the scope of the invention as described in thespecification and defined in the appended claims.

We claim:
 1. A method of making an integral structure comprised of innerand outer coaxial shells mutually supported so as to define an annularpassageway therebetween comprising the steps of:(a) braiding on a shapedmandrel a plurality of fibers to form an inner shell preform having anouter surface being substantially a surface of revolution; (b) braidingon a conical mandrel a plurality of fibers to form a duct preform havinga conical shape; (c) removing the duct preform from the conical mandrel;(d) administering each of a plurality of the duct preforms formed instep (b) onto an outer peripheral surface of a duct mold having a shapedifferent from that of the conical mandrel so as to contiguously conformto the shape of the duct mold and thereby define a modified duct preformincluding an inner duct surface shaped to congruently mate with theouter surface of the inner shell preform, an outer duct surface spacedfrom the inner duct surface, and first and second lateral walls havingopposed lateral surfaces; (e) mounting the plurality of the modifiedduct preforms together with their associated duct molds onto the outersurface of the inner shell preform in side-by-side relationship suchthat the first and second lateral surfaces on adjacent modified ductpreforms are coextensive and engaged, the plurality of the modified ductpreforms completely circumscribing the inner shell preform; (f) braidinga plurality of fibers across the plurality of outer duct surfaces toform an outer shell preform spaced from and coaxial with the inner shellpreform and to integrally encapsulate the outer duct surfaces; (g)applying resin to structure defined by the braided inner shell preform,the braided modified duct preforms, and the braided outer shell preformto fill all voids in the structure; and (h) curing the resin to therebyform an integral structure comprised of inner and outer shells and aplurality if circumferentially spaced strut members defined by theengaged first and second lateral walls of the adjoining modified ductpreforms.
 2. A method of making an integral structure as set forth inclaim 1wherein the inner shell preform has a generally cylindricalpassage extending therethrough and extends between an annular leadingend and an annular trailing end; and including the steps of: (i)administering to the annular leading end a first annular metallic endplate with fastener means thereon in proximate engagement therewith; (j)administering to the annular trailing end a second annular metallic endplate with fastener means thereon in proximate engagement therewith; and(k) during step (a), braiding a plurality of the fibers so as tointertwine the first and second end plates for fixation thereof to theinner shell preform.
 3. A method of making an integral structure as setforth in claim 2wherein the outer shell preform has an outermost surfacebeing substantially a surface of revolution and extends between anannular leading end and an annular trailing end; and including the stepsof: (l) administering to the annular leading end of the outer shellpreform a third annular metallic end plate with fastener means thereonin proximate engagement therewith; (m) administering to the annulartrailing end of the outer shell preform a fourth annular metallic endplate with fastener means thereon in proximate engagement therewith; and(n) during step (f), braiding a plurality of the fibers so as tointertwine the third and fourth end plates for fixation thereof to theouter shell preform.
 4. A method of making an integral structure as setforth in claim 3 including the steps of:(o) administering to theoutermost surface of the outer shell preform an outer mold in contiguousengagement therewith; (p) placing a forward end cap in contiguousengagement with the first and third end plates; (q) placing a rear endcap in contiguous engagement with the second and fourth end plates; (r)supporting the forward and rear end caps between spaced apart forwardand rear press plates, respectively; and wherein step (g) includes thestep of: (s) applying resin through apertures in the forward and rearpress plates and through apertures in the forward and rear end caps tofill all voids in the braided inner shell preform, the braided ductpreforms, and the braided outer shell preform.
 5. (Amended) A method ofmaking an integral structure as set forth in claim 4 including the stepsof:(t) withdrawing the forward and rear end plates from engagement withthe forward and rear end caps, respectively; (u) withdrawing the forwardend cap from contiguous engagement with the first and third end plates;(v) withdrawing the rear end cap from contiguous engagement with thesecond and fourth end plates; (w) withdrawing the shaped mandrel fromthe formed inner shell; (x) withdrawing each of a plurality of the ductmolds from the regions defined by the formed inner shell, the formedouter shell, and the circumferentially spaced strut members; and (y)withdrawing the outer mold from its contiguous engagement with theoutermost surface of the outer shell.
 6. A method of making an integralstructure as set forth in claim 1 wherein:the plurality of fibersutilized in steps (a) and (f) are comprised of graphite.
 7. A method ofmaking an integral structure as set forth in claim 1 wherein:theplurality of fibers utilized in steps (a) and (f) are comprised ofboron.
 8. A method of making an integral structure as set forth in claim1 wherein:the plurality of fibers utilized in steps (a) and (f) arecomprised of glass.
 9. A method of making an integral structure as setforth in claim 1 wherein:the plurality of fibers utilized in steps (a)and (f) are comprised of aramid fibers.
 10. A method of making anintegral structure comprised of an outer shell coaxially supported on aninner member having an outer surface which is substantially a surface ofrevolution so as to define an annular passageway between the innermember and the outer shell comprising the steps of:(a) braiding on aconical mandrel a plurality of fibers to form a duct preform having aconical shape; (b) removing the duct preform from the conical mandrel;(c) administering each of a plurality of the duct preforms onto an outerperipheral surface of a duct mold having a shape different from that ofthe conical mandrel so as to contiguously conform to the duct mold andthereby define a modified duct preform including an inner duct surfaceshaped to congruently mate with the outer surface of the inner member,an outer duct surface spaced from the inner duct surface, and first andsecond lateral walls having opposed lateral surfaces; (d) mounting theplurality of the modified duct preforms together with their associatedduct molds onto the outer surface of the inner member in side-by-siderelationship such that the first and second lateral surfaces on adjacentmodified duct preforms are coextensive and engaged, the plurality of themodified duct preforms completely circumscribing the inner member; (e)braiding a plurality of fibers across the plurality of outer ductsurfaces to form an outer shell preform spaced from and coaxial with theinner member and to integrally encapsulate the outer duct surfaces; (f)applying resin to a structure defined by the braided modified ductpreforms and the braided outer shell preform to fill all voids in thestructure; and (g) curing the resin to thereby form an integralstructure comprised of inner member and outer shell and a plurality ofcircumferentially spaced strut members defined by the engaged first andsecond lateral walls of the adjoining modified duct preforms.
 11. Amethod of making an integral structure as set forth in claim 10 whereinstep (a) includes the steps of:(h) braiding the plurality of fibers toform an inner layer of an inner shell preform extending between aleading end and a trailing end; (i) providing a first metallic annularend plate with fastening means thereon adjacent the leading end of theinner shell preform; (j) providing a second metallic annular end platewith fastening means thereon adjacent the trailing end of the innershell preform; (k) braiding a plurality of fibers to form an outer layerof the outer shell preform and intertwining the first and second annularend plates for fixation thereof to the inner shell preform; (l) applyingresin to a structure defined by the braided modified duct preforms andthe braided outer shell preform to fill all voids in the structure; and(m) curing the resin to thereby form an integral structure comprised ofthe inner shell and the outer shell and a plurality of circumferentiallyspaced strut members defined by the engaged first and second lateralwalls of the adjoining modified duct preforms, the first and secondannular end plates enabling attachment of the integral structure toother components.